The effect of transgene expression on the regulation of hematopoiesis was examined in transgenic mice in which the Ets2 gene was driven by the mouse metallothionein promoter. It has been found that transgene expression results in an increase in the number of cells from bone marrow and spleen capable of forming colonies in semisolid media containing IL-3. The transgenic mice were found to have a higher percentage of megakaryocytes in their bone marrow than control animals. Bone marrow cultures derived from transgenic animals express higher levels of the c-mpl gene as compared to normal controls. c-mpl codes for the receptor for the platelet-inducing cytokine, thrombopoietin.